Methacrylic resin composition has superior transparency and weather durability. The methacrylic resin composition is utilized as a molding material for a light guide plate, which is used as a member of a backlight unit for various types of liquid crystal displays, or for vehicle members such as a rear lamp cover, a head lamp cover, a meter panel, and so on (See Patent Literatures 1 and 2).
As a methacrylic resin composition, there is a known composition containing a higher molecular weight polymer and a lower molecular weight polymer (See Patent Literatures 3-7). The methacrylic polymer composition containing both of the higher molecular weight polymer and the lower molecular weight polymer has advantages such as a broader molecular weight distribution as well as a superior solvent resistance and a superior flowability for molding. As a method for producing a methacrylic resin composition comprising a higher molecular weight polymer and a lower molecular weight polymer, some methods are suggested such as a method comprising an addition of methyl methacrylate and methyl acrylate in the presence of a methacrylic resin obtained by a suspension polymerization, and a subsequent suspension polymerization (See, for example, Patent Literature 3); a method comprising a bulk polymerization and a subsequent additional bulk polymerization by adding an initiator and a chain transfer agent (See, for example, Patent Literature 4), and a method comprising separate preparing of methacrylic resins having different average molecular weights, respectively, and subsequently blending the separately prepared resins (See, for example, Patent Literatures 5-7), etc.